The present invention relates to improvements in apparatus for heating plastic or like materials, and more particularly to improvements in apparatus of the type disclosed in commonly owned copending patent application Ser. No. 451,337 of Nolle et al. for "Inductively operated heating apparatus for plastic materials", now U.S. Pat. No. 5,003,145 granted Mar. 26, 1991. The disclosure of the copending application Ser. No. 451,337 is incorporated herein by reference.
It is known to provide an inductively operated heating apparatus for plastic materials with a housing which is made of steel and has one or more passages for the material to be heated. The magnetic field of the apparatus is established by laminated iron cores which are magnetically coupled with the housing and have legs extending toward the housing. At least one leg of each core carries a winding. Apparatus of the just outlined type and disclosed, for example, in the aforementioned copending patent application Ser. No. 451,337, can be used with advantage in extruding machines for plastic materials.